To say that Bitcoin can maintain a higher price point than a future coin that forms a bigger network, seems similar to me thinking I can beat the house at blackjack.
Is there something I'm missing about the "digital gold" theory?
What you seem to be missing is the point that we just cannot know what the future holds.
Bitcoin is the biggest now, still. And this means that Bitcoin is still the best suited for the job whatever others claim.
When others will face the difficulties Bitcoin
seems to face now ("too" high number of transactions, rising tx cost, ruthless competitors), Bitcoin will have been solved them.
I don't say that in the future a better coin can rise. But when? Many need a store of value
now.